Question

Solve x + 3y = 9 3x − 3y = −13

Answer 1

X + 3y = 9
3x - 3y = -13
---------------------  add the equations
4x  = -4
divide both sides by 4
x = -1

plug -1 back into either equation and solve for 'y'.
x + 3y = 9
-1 + 3y = 9
add 1 to both sides
3y = 10
divide both sides by 3
y = 10/3 or y = 3 1/3

(-1, 10/3), OR (-1, 3 1/3)

Answer 2

X + 3y = 9
3x - 3y = -13
--------------add
4x = - 4
x = -4/4
x = -1

x + 3y = 9
-1 + 3y = 9
3y = 9 + 1
3y = 10
y = 10/3

solution (-1,10/3)